The present invention generally relates to inspection systems, and more particularly to an electric current perturbation probe having omni-directional sensitivity capabilities.
Inspection systems having eddy current probes are often used for non-destructive evaluation (NDE) of critical components in the aerospace and power generation industries. Many components in these industries must endure extremely high stresses in the course of operation. It is necessary to detect even minute flaws in order to ensure the durability of these components. For example, a rotor disk for a gas turbine engine must have its entire surface inspected in order to detect the presence of defects. An inability to detect defects of a certain size or orientation can prevent the production of higher performance and more competitive products, and may lead to safety concerns regarding the product.
Known eddy current probes typically include a driver coil and at least one receiver coil. The driver coil is provided with an electrical excitation signal (i.e. an electrical current) and generates an alternating electromagnetic field that results in a magnetic field in a component under inspection as the probe is moved along a path above the component's surface. The magnetic field creates an eddy current in and near the surface of a component fabricated from a conductive material. The eddy currents in the component under inspection result in an electromagnetic signal or response, which is received within the receiver coil and detected by commercial instrumentation. As the eddy current probe passes over an anomaly, e.g., a flaw or a different morphology in the component, the anomaly disrupts the eddy currents and results in a different signal received by the receiver coil. The change between the signal received by the receiver coil and the signal generated within the driver coil is detected by the commercial instrumentation.
One type of eddy current probe is referred to as an electric current perturbation (ECP) probe. An ECP probe defines a driver core axis which is perpendicular to a receiver core axis. This feature decouples the driver magnetic field from a receiver, thereby reducing the sensitivity of the receiver to surface noise that does not represent a defect.
Although ECP probes typically provide high sensitivity, these probes are directionally sensitive in a single direction. That is, known ECP probes have a unidirectional sensitivity characteristic. Therefore, the ECP probes may only detect a flaw in the component where the orientation of the flaw is aligned directly with the directional sensitivity of the probe. Many components include complex surfaces that define complicated part stresses which may include flaws having an arbitrary orientation which is not aligned with the directional sensitivity of the electric current perturbation probe. Disadvantageously, the arbitrary orientation of the flaw may result in the flaw being unidentified by the electric current perturbation probe. The inability to detect flaws of a certain orientation can prevent production of higher performance and more competitive products, and may lead to safety concerns.
Accordingly, it is desirable to provide an omni-directional electric current perturbation probe that achieves increased sensitivity and that is disruptible in multiple directions.